Heavyweight Candidate for Dark Matter

Watching Dark Matter: This photo is a montage of several images and shows colliding galactic clusters, commonly known as "Bullet Cluster" (1E 0657-56). The galaxies visible in the optical light of the background image are covered with X-rays from intergalactic gas clouds (pink), as well as the mass distribution calculated from the gravitational effects of the lenses and therefore the indirect dark matter (blue). Credit: NASA / CXC / M. Weiss

Nearly a quarter of the universe is literally in the shadows. According to the theories of cosmologists, 25.8% of it consists of dark matter whose presence is signaled essentially only by its gravitational pull. What this substance consists of remains a mystery. Herman Nikolai, director of the Max Planck Institute for Gravitational Physics in Potsdam, and his colleague Krzysztof Meissner of Warsaw University have already proposed a new candidate – ultra-heavy gravity. The existence of this still hypothetical particle follows from a hypothesis that seeks to explain how the observed spectrum of quarks and leptons in the standard model of particle physics can emerge from a fundamental theory. In addition, the researchers describe a possible method for actually tracking this particle.

The standard model of particle physics encompasses the building blocks of matter and the forces that hold them together. It states that there are six different quarks and six leptons, which are grouped into three "families". However, the matter around us and ourselves ultimately consists of only three particles from the first family: the up and down quarks and the electron that is a member of the lepton family.

So far, this long-established standard model has remained unchanged. The Large Hadron Collision (LHC) at CERN in Geneva was commissioned about ten years ago with the primary purpose of exploring what might be outside it. However, after ten years of data acquisition, scientists were unable to find new elementary particles other than the Higgs boson, despite widespread expectations to the contrary. In other words, measurements with the LHC so far have not given any hint of "new physics" beyond the standard model. These findings are in sharp contrast to the numerous proposed extensions of this model, which suggest a large number of new particles.

In an earlier article published in Physical Review Letters Hermann Nicholas and Krzysztof Meissner presented a new hypothesis that seeks to explain why only known elementary particles are found as essential building blocks for nature – nature's building blocks Contrary to previous thinking, no new particles are expected in the energy range available for current or possible future experiments

In addition, the two researchers postulate the existence of supermassive gravity, which could be extremely unusual candidates. dates for dark matter. In a second publication that recently appeared in Physical Review D they also put forward a proposal for how to track these gravity down.

In their work, Nicholas and Meissner adopt an old idea from Nobel Prize winner Murray Gel-Mann, which is based on the theory "N = 8 Super Gravity". One of the key elements of their proposal is a new type of boundless symmetry that aims to explain the observed spectrum of known quarks and leptons in three families. "Our hypothesis does not actually produce additional particles for ordinary matter, which should then be disputed, because they are not shown in accelerator experiments," says Hermann Nicholas. "Unlike us, our hypothesis can in principle explain exactly what we see, in particular the replication of quarks and leptons in three families."

However, processes in the cosmos cannot be fully explained by ordinary matter, which we are already aware of. One sign of this is the galaxies: they spin at high speed, and visible matter in the universe – which represents only 5% of the matter in the universe – would not be enough to hold them together. So far, however, no one knows what the rest is made of, despite numerous suggestions. The nature of dark matter is therefore one of the most important unanswered questions in cosmology.

"The general expectation is that dark matter is composed of an elementary particle and that it has not yet been possible to detect this particle because it interacts with ordinary matter almost exclusively by gravitational force," says Hermann Nicholas. The model, developed in collaboration with Krzysztof Meissner, offers a new candidate for dark matter of this type, though with completely different properties from all candidates discussed so far, such as axions or WIMPs. The latter interact very poorly with known matter. The same applies to the very light gravity, which has repeatedly been offered as a candidate for dark matter in connection with low energy supersymmetry. However, this proposal goes in a completely different direction, since it no longer assigns a major role to over-symmetry, although the scheme originates from a maximum of N = 8 super gravity. "In particular, our scheme foresees the existence of superheavy gravity, which – unlike the usual candidates and unlike the previously considered light gravity – would also interact strongly and electromagnetically with ordinary matter," says Hermann Nicholas.

Their large mass means that these particles could only occur in a very dilute form in the universe; otherwise they would "shut down" the universe and thus lead to its early collapse. According to researcher Max Planck, one really won't need many of them to explain the content of dark matter in the universe and in our galaxy – a fraction of 10,000 cubic kilometers would be enough. The mass of particles postulated by Nicholas and Meissner is located in the area of ​​Planck's mass – that is, about one hundred million kilograms. For comparison, protons and neutrons – the building blocks of the atomic nucleus – are about ten quintillion (ten million trillion) times lighter. In intergalactic space, the density will be even much lower.

"The stability of these heavy gravitas depends on their unusual quantum numbers (charges)," says Nikolai. "In particular, in the standard model, there will be no definitive states with corresponding charges in which these gravitas could collapse – otherwise they would disappear shortly after the Big Bang."

Their strong and electromagnetic interactions with known matter can make these dark matter particles easier to trace, despite their extreme rarity. One option is to look for them with special measurements in deep-underground flight, as these particles move much slower than the speed of light, as opposed to the ordinary elemental particles originating from cosmic radiation. However, they would penetrate Earth effortlessly because of their large mass – like a cannon ball that cannot be stopped by a swarm of mosquitoes.

This fact gives the idea to the researchers to use our planet as a "paleo-detector": "Earth orbits through the interplanetary space for about 4.5 billion years, during which time many of these massive gravitas must have penetrated In the process, particles must leave long, straight ionization traces in the rock, but it may not be easy to distinguish them from traces caused by known particles. "Ionizing radiation is known to cause lattice defects in crystalline structures. It is possible that relays are found such ionization traces in crystals that have remained stable for millions of years, "says Hermann Nicholas. Because of its long" exposure time ", such a search strategy may be successful even if dark matter is not homogeneously distributed within in the galaxies, but is subject to fluctuations in local density – which may also explain the failure of the search for more conventional dark matter candidates so far.